1. Field of Invention
The invention relates to a displaying device and, in particular, to a liquid crystal displaying device with a backlight unit.
2. Related Art
Regarding to the application fields, the liquid crystal displaying devices are used for monitors or televisions. In fact, the structures of the liquid crystal displaying devices used for monitors and televisions are similar, and only different in several components, circuits and the layout of some components.
With reference to FIG. 1, a conventional liquid crystal displaying device 1 includes a liquid crystal displaying (LCD) panel 11, a backlight unit 12, a driving circuit 13, a control circuit 14, a first shell 15, a second shell 16, and a stand 17.
As shown in FIG. 1, the liquid crystal displaying panel 11 at least includes a liquid crystal layer 111, a color filter substrate 112, a thin film transistor (TFT) circuit substrate 113, and two polarizers 114 and 115. The liquid crystal layer 111 is disposed between the color filter substrate 112 and the TFT circuit substrate 113. The polarizer 114 is disposed at one side of the color filter substrate 112, while the polarizer 115 is disposed at one side of the TFT circuit substrate 113.
Referring to FIG. 1 again, the backlight unit 12 includes a lamp case 121 and a power driver 122 for driving lamps. The lamp case 121 at least includes a plurality of lamps 120 and a diffuser 124.
The driving circuit 13 electrically connects to the LCD panel 11 for driving the LCD panel 11. In general, the driving circuit 13 is composed of a plurality of driving ICs 131 and at least one driving circuit board 132.
The control circuit 14 is used for controlling the driving circuit 13 so as to control the LCD panel 11. The control circuit 14 and the power driver 122 are commonly installed at one side of the lamp case 121. The lamp case 121 is positioned adjacent to the LCD panel 11, so that the lamps 120 of the lamp case 121 can illuminate the LCD panel 11.
As shown in FIG. 1, the LCD panel 11, backlight unit 12, driving circuit 13 and control circuit 14 are encapsulated with the first shell 15 and the second shell 16. Herein, the second shell 16 connects to the stand 17.
In view of the above-mentioned liquid crystal displaying device 1, a plurality of lamps 120 are installed in the lamp case 121, and are usually cold cathode fluorescent lamps (CCFL). Due to the variation of lifetime and quality among CCFLs, if any one of the lamps 120 malfunctions, the entire backlight unit 12 may cause problems with providing illumination. The worst case would be the whole liquid crystal displaying device must be discarded. For solving this problem, a lamp case 121 with special structure is invented recently, which makes it possible to replace one single lamp 120 within the invented lamp case. This structure might provide the solution for replacing the lamp 120, however, it still cannot solve other two problems. The first problem is that since there are a plurality of lamps 120 installed in the lamp case 121, there's loss of uniformity between the brightness of the newer lamp(s) 120 and the brightness of older lamps 120 once after one or two lamps 120 are replaced. Regarding to the second problem, since the LCD panel 11, backlight unit 12, driving circuit 13 and control circuit 14 are encapsulated with the first shell 15 and second shell 16, the first shell 15 and second shell 16 must be disassembled before replacing the lamp(s) 120. In some cases, the control circuit 14 and power driver 122 must also be uninstalled before replacing the lamp(s) 120. The disassembling or uninstalling process might be simple for the professionals, but for the general users, it could be very difficult. Not to mention this process may cause damage to the products. On the other hand, since the lamps are driven by high voltage, it is not safe for the users to perform the above-mentioned process themselves.
Regarding to the above-mentioned descriptions, the CCFL is just one example of the light-emitting element used for the backlight unit. To be general, the light-emitting element of the backlight unit can be a light-emitting diode (LED) or a flat fluorescent lamp (FFL).
Therefore, it is an important subject of the invention to provide a liquid crystal displaying device, which can facilitate the replacement of light-emitting elements of the backlight unit, retain the brightness uniformity of the backlight unit, and the lifetime thereof.